Abstract:
Nuttalliella namaqua is the only species of the enigmatic third tick family. Females possess features of hard and soft ticks
and have been designated as the ‘‘missing link’’ between the main tick families. Its position at the base of the tick tree
suggests that some of the features unique to hard and soft ticks were present in the ancestral tick lineage. Larvae, nymphae
and males have not been described to date and questions regarding their biological affinities to the main tick families
remain unclear. The current study addressed these questions via the description of larvae, nymphae and males and resolved
issues pertaining to female morphology. Field collected as well as laboratory-engorged females laid eggs and viable larvae
subsequently hatched. The larvae possess morphological structures not present in subsequent stages: namely, a sclerotized
scutum, pores on the dorsal surface of legs and a dentate anal plate. The last two characters are not present in ixodids and
argasids. N. namaqua larvae and nymphae show a similar morphology to females: a unique hypostomal structure i.e.,
bluntly rounded apically in nymphae and females and ball-like in the larvae. A re-description of some structures in female N.
namaqua has resolved differences in the original descriptions, namely that N. namaqua have 4 palpal segments as found in
ixodids and argasids and posthypostomal setae. The male was discovered for the first time and described. Characteristic
male features include: a pseudoscutum over most of the dorsum, an outgrowth on the chelicerae forming a unique rod-like
structure similar to a spematodactyl in mites and medial extension of palpal segment 2 forming a large ventral crib for
segment 4. All life stages possess some features found in hard and soft ticks and its status as the ‘‘missing link’’ between the
tick families remains.
